This invention relates to a process whereby an anchor which can be pre-stressed and re-tightened is fixed into a hole in rock.
The fitting of earth and rock anchors into a borehole in such a way as to leave no gap between the tension member and the borehole is possible only by injection moulding. In anchors produced in this way, in which the tension members are generally made of steel, the risk of corrosion is high. Cracks may occur in the injection moulded body due to excessive localised tension and changes in length may occur in the event of shifting of the ground. The tension member is then very liable to be attacked by corrosion in this region. With the known adhesive cartridges it is impossible to assess accurately the length to which the force is introduced. When systems containing filler are used in these cartridges, it is frequently impossible to obtain a homogeneous mixture. Anchoring overhead, as when a tension member has to be fixed to a roof, is then particularly unreliable. Very active adhesive systems must then be used, but these do not have the necessary high quality bonding properties. When hydraulic mortar is used for injection moulding, a major proportion of it is first injected and is then partly rinsed off so that a part of the tension member is again exposed. This is a very expensive process.